Biomedical leads (including electrodes) are a primary component of many implantable medical devices including cardiac pacemakers and defibrillators, deep brain stimulation devices, cochlear implants, peripheral nerve (sacral, phrenic, vagal, etc.) stimulation devices, and spinal cord stimulation devices for pain management. The lead is used to transmit electrical signals to and from a device interface (e.g. a pulse generator) and one or more electrodes located near the tip or within the body of the lead (as shown in FIG. 1) and which is implanted into the appropriate target tissue (brain, nerve, muscle, heart, etc.), and a device interface.
Many implantable biomedical devices require quick, efficient, and accurate signal transduction through the lead in order to appropriately monitor and record bio-electrical activity, and to deliver therapeutic electrical signals. For example, cardiac pacemakers and cardiac resynchronization therapy electrically monitor the heart's activity and then deliver electrical pulses to regulate cardiac contractions. Deep brain stimulators are used to monitor neural activity and deliver therapeutic pulses to prevent the dyskinesia associated with Parkinson's disease, or to detect and/or prevent the onset of a seizure. Spinal cord stimulation involves the delivery of electrical pulses to electrodes implanted in or near the spinal cord in order to counteract chronic pain. Cochlear implants provide auditory sensation to persons with severe hearing loss by sending acoustic information in the form of electrical signals to an array of small metal electrodes implanted within the cochlear structure in the inner ear. Electrical signals sent to the vagus nerve, sacral nerve, and other targets in the peripheral nervous system are used to treat a number of diseases and disorders such as obesity, chronic pain, urinary incontinence, loss of diaphragm control, heart failure, and hypertension. Implantable cardio-defibrillators monitor cardiac activity and upon observing heart failure deliver large electrical shocks to restore cardiac function.
A major concern with such conventional leads is fracture. The consequences of lead fracture can be quite severe. In the case of implantable cardioverter defibrillators (ICDs), lead fracture produces inaccurate sensing of cardiac activity which can result in either inappropriate shock of the patient—a painful and traumatic experience that can damage the heart or surrounding tissue—or worse, the device can fail to shock when needed, possibly leading to death of the patient.